1. Field of the Invention
The present invention relates to the surgical treatment of chondral defects and, more specifically, to apparatus for autogenous or allograft transplantation of articular cartilage/bone cores in knees having chronic anterior cruciate ligament (ACL) deficiency, or isolated articular defects.
2. Description of the Related Art
As shown in FIG. 1, windows 11 and depth markings 12 are provided on the tube of the donor site harvester along the portion of the tube where the bone core is received to assist the surgeon during insertion of the harvester into the bone at the donor site. A longitudinal marking line (not shown) provided at the top of each harvester facilitates core alignment in the recipient socket.
Chondral defects of the femoral condyles are widely recognized indications which comprise approximately 5% of all knees undergoing arthroscopy. Treatment, however, is difficult and controversial. In earlier known methods, meniscal pathology was treated, and the ACL was reconstructed, but the chondral lesion usually was left untreated. This approach leads to lesion enlargement and ultimately an advancing arthritic condition.
A protocol of arthroscopic osteochondral autograft transplantation for repairing chondral defects has been developed and tested in knees having chronic ACL deficiency by Vladimir Bobixc4x87, as reported in Arthroscopic Osteochondral Autograft Transplantation In ACL Reconstruction: A preliminary clinical study; Knee Surgery, Sports Traumatology Arthroscopy (1996), incorporated herein by reference.
The transplantation procedure, which is intended to prevent further joint degeneration and possible development of osteoarthrosis, involves selecting donor sites for osteochondral cores, capped with intact cartilage, prior to notchplasty. Donor sites are selected along the anterolateral and superior aspect of the notchplasty area, or on the superolateral and anterolateral aspect of the lateral femoral condyle in the non-weightbearing area above the sulcus terminalis. At the donor sites, multiple osteochondral cores 5 mm to 9 mm in diameter and 10 to 15 mm long, are harvested using tubular cutting instruments.
Recipient repair sites typically are located on the weightbearing area of the medial and lateral femoral condyles. Full-thickness chondral defects, typically larger than 10 mm in diameter, and up to 20 mm, are selected for treatment. Recipient sockets at the repair sites are prepared, and the donor cores are transferred and press-fitted into the recipient sockets.
The transplantation procedure described above has various difficulties associated with it. For example, removing the osteochondral cores from the tubular cutting instruments is difficult. In addition, improvements are needed in the formation of the donor cores and recipient sockets, especially to facilitate depth control during harvest, as well as transplant removal and insertion. In general, improvements are required in the instrumentation and techniques available to perform the transfer procedure.
The present invention overcomes the deficiencies in the prior art by providing surgical instruments for performing osteochondral transplant procedures using a series of thin-walled (0.5 mm) cutting tubes. Osteochondral cores, made up of hyaline cartilage capping subchondral bone, are harvested, either autogenously or as allografts. The osteochondral cores, preferably 10 to 15 mm in length, are transplanted into sockets created in the defect to accept the transplanted core, or multiple cores, in a press-fit manner. The instruments allow the technique of the present invention to be carried out as either an open procedure or arthroscopically. Determinations regarding the protocol used will be based, for example, on the location, geometry, and extent of the chondral defect and the harvest sites.
The instrumentation of the present invention includes a series of core harvesters. The harvester of the present invention preferably includes a hollow tube having a distal cutting edge and a cannulated handle attached proximally. Within each core harvester, a collared pin is disposed slidably to facilitate removal of the harvested osteochondral core. The collared pin acts as a plunger to urge the harvested core from the lumen of the core harvester tube, and preferably has a concave face for enhanced biomechanical contact with the curved surface of the harvested core.
Preferably, two types of harvesters are provided: a donor harvester for obtaining donor osteochondral cores, and a recipient site harvester for forming recipient sockets at repair sites.
Advantageously, the inner diameter of the donor harvester is equal to the outer diameter of the recipient site harvester. The outer diameters differ by 1 mm to accommodate the 0.5 mm wall thickness. The thin walls minimize bone and tissue damage.
The harvesters are provided in a range of sizes. To assist in harvesting to the proper depth, markings are provided on the instruments. The markings preferably are located on the outer surface of the harvester tubes for direct visual alignment with the surface of the tissue being harvested. Slotted windows are provided through the side walls of the tube to allow visualization of the harvested osteochondral core within the lumen of the harvester tube, allowing for visual confirmation of core length and surface geometry, for example, and for visual confirmation of depth during insertion.
The two types of bone harvesters can be distinguished by the formation of the sharp, distal cutting edge. On the donor graft harvesters, the distal cutting edge preferably is formed as a dual bevel, such that the cutting edge is formed by two 10xc2x0 slanted surfaces sloping distally from the inner and the outer surfaces. The two bevels meet to form the cutting edge. Accordingly, the acutely-angled cutting edge is formed at the junction between the outer beveled surface and the inner beveled surface of the harvester tube wall. Accordingly, the donor harvester slightly compacts the bone core during harvesting.
On the recipient site harvesters, the distal cutting edge preferably is formed with a bevel which is formed by a slanted surface that slopes distally and outward from the central axis, from the inner surface to the outer surface of the harvester tube wall. Accordingly, the acutely-angled cutting edge is formed between the inner, beveled surface and the outer surface of the harvester tube wall.
The two harvesters cooperate for precise correspondence in size between the donor graft and the recipient site. Advantageously, the dual bevel on the donor harvester provides a slight compression, which results in a desirable press fit of the donor upon insertion into the correspondingly-sized recipient socket. Correct sizing avoids problems associated with an improper fit of the graft in the recipient site, including over-compression or insufficiency of the repair.
According to a preferred method, the donor harvester is inserted into a tube harvester driver/extractor and placed over the selected hyaline cartilage harvest site. The donor harvester is placed flush with the articular cartilage surface and impacted, using a mallet for example, to a selected depth of approximately 10 to 15 mm. After complete insertion to the selected depth, the driver/extractor is twisted and gently rocked to fracture the cancellous base for removal of the osteochondral core.
A recipient site is prepared with a recipient site harvester using a similar method. Alternatively, recipient sockets can be formed using various techniques, such as by drilling. The donor core preferably is pressed into the recipient site directly from the donor harvester.
Prior to insertion, size correlation between the donor core and the recipient site is provided by using a graft sizer and an alignment stick. The depth of the recipient site is determined using the alignment stick. If the graft osteochondral core is too long, adjustment of the core length or the length of the recipient site can be effected accordingly.
Using the driver/extractor, the donor osteochondral core is advanced with the collared pin so that the distal end of the core is flush with the end of the cutting edge of the harvester tube. As a manual aid to insertion depth control, the collared pin is sized so that the proximal end comes flush with the proximal end of the harvester handle when the distal end of the collared pin is 1 mm recessed from the cutting edge of the cutting end of the bone harvester. Accordingly, nearly-flush, anatomical insertion of the cartilage/bone core can be obtained without direct visual observation, and over-insertion is avoided.
In an alternative arrangement, the harvested donor bone graft is pressed using the collared pin into a rigid, transparent graft transfer tube, preferably made of plastic. The graft transfer tube allows visualization of the transfer procedure and provides increased confidence in performing the graft procedure.
After insertion, the osteochondral core insert is brought flush anatomically using a sizer/tamp. The graft is pressed with the sizer/tamp such that the surface of the graft comes into flush alignment with the normal articular cartilage surrounding the recipient repair site.
Although the instruments and techniques are described herein in connection with a specific autograft application in the ACL-deficient knee, they can be applied to ACL-normal knees, for treatment of joints other than the knee, and for xenogenous procedures. In addition, indications for the instrumentation and techniques of the invention can be extended to include other treatments, such as, for example, osteochondritis dissecans, allograft transplantation, bone grafting, graft fixation, and focused bone core biopsy.
Other features and advantages of the present invention will become apparent when the following description is read in conjunction with the accompanying drawings.